The purpose of this study was to perform a sub-acute toxicologic evaluation of the antiprogestational drug, CDB-2914, prior to initial clinical investigation in women. Twelve animals were randomly assigned to a control, low, or high dose group of four animals each. The high and low dose groups received CDB-2914 by naso-gastric intubation once per day for fourteen days at 100 mg/kg weight and 20 mg/kg weight respectively. The control group received the vehicle at 1 ml/kg weight. Eleven of the twelve animals were euthanized on day fifteen of the study, with one animal from the high dose group euthanized on day eight due to her critical condition. Animals were weighed prior to initial treatment, once per week during treatment, then on their necropsy date. All animals had hematology, blood chemistries and urinalysis done at their respective necropsy date. A single pre-treatment and daily post-treatment blood samples were obtained for analysis of test article and cortisol. A gross necropsy was conducted, with organs and tissues fixed in formalin and stained for histopathology. There were adverse effects in the high dose group, with less severe effects in the low dose group, which indicated a dose-related toxicity. Two animals from the high dose group were taken off treatment due to debilitated health. One of the animals had improved health after receiving medical treatment and was placed back onto treatment after missing two daily treatments. However, the other animal did not improve with medical treatment and euthanasia was elected. In addition to adverse physical signs, increased organ weights, some abnormal serum biochemistry and urinalysis parameters, an increase of cervical mucous cells and decrease in bone marrow cellularity suggest that specific organs were targets of toxicity. *KEY*Anti-progestin, Post-coital contraception